The present disclosure is directed to a wireline supported perforating mechanism, and more particularly to a perforating gun. It is intended for use in a slant well. It is especially intended to line up the perforations with a particular orientation relative to the formation which is tranversed by the slant well.
It is not uncommon to drill slant wells, especially from offshore platforms and the like. For instance, once a producing field has been discovered, one of the next steps is to install a platform at a proper location in the field. The platform may support the well head equipment for numerous wells, perhaps as many as sixty-four. Needless to say, while all sixty-four wells may come together at the platform, they terminate at multiple locations across the formation of interest. This involves the drilling of slant wells from the platform. Several slant wells are drilled in which a substantial portion of the well is inclined from the vertical. It is not uncommon to have an inclination as much as fifty, sixty or even seventy degrees deviation from the vertical. The present apparatus is particular adapted for perforating on the slant where the perforating apparatus to be described is operated. There is another factor which creates a severe handicap to flow from the perforations. This relates to the direction of the formation which is traversed by the slant well. The well will pass through many formations. In the simplest of cases, the well is assumed to be vertical, and the formations are assumed to be parallel planes arranged horizontally with respect to the well and which are intersected perpendicularly. However, many formations which provide greater production include those which are arranged at different angles as a result of various geological events. In particular, the formations can slope upwardly or downwardly with respect to a horizontal reference plane. They might be as much as forty, fifty or even sixty degrees inclined from the horizontal reference. Moreover, formations have a type of grain which extends through them. This is sometimes known as the formation bedding plane or the fracture plane. These are planes which are found within the formation and which define a preference for production fluid flow. In fact, the preference can be so strong that one can think of the formation as having a grain in the same sense as wood. Heretofore, it has been impossible to lower a perforating gun on a wireline to a particular formation and operate that perforating gun so that perforations are accurately positioned at an angle where the perforations are parallel to the bedding plane of the formation. In other words, there has been no known approach for positioning the perforations so that they extend along the grain of the formation with surface, real time verification of position. The present disclosure sets forth a method and apparatus for accomplishing this.
This disclosure is directed to a wireline tool which can be lowered into a well borehole, typically a cased well, and can be lowered even into the slant portion. It is lowered to a depth sufficient to locate the perforating gun assembly opposite the formation of interest. The present apparatus further includes means functioning in the fashion of a pendulum which seeks the vertical gravity vector thereby defining a horizontal reference plane and further includes means permitting the perforating gun to be aligned with respect to the formation so that perforations are formed in the desired manner. In other words, the perforations are formed at the requisite well depth in the formation of interest, and the perforations extend parallel to the grain of the formation to thereby enhance production. This enables that type of orientation to be achieved.
The present tool is summarized as a wireline tool which is supported on a wireline cooperative with a casing collar locator and navigation apparatus. There is an elongate cylindrical sleeve gun tape which supports one or more shaped charges for forming perforations. That is connected with an eccentric which defines a weight at an adjustable angular position. All of the foregoing is able to rotate between upper and lower cradle assemblies which are equipped with rollers on sleeve line rotors. This allows the weight to fall to the low side as the tool is positioned in the slant well, which operates in the fashion of a plumb bob to seek the vertical. Appropriate perforating gun firing circuitry and other equipment is also included. More will be noted regarding the details of the structure hereinafter.